In my copending U.S. patent application Ser. No. 07/266,014, filed Nov. 2, 1988, for Method of Producing Metal Oxide Super-Conducting Polymer Composites Wherein Radiation-Sensitive Resist Polymer-Metal-Complex Precursors Form Interconnected Superconducting Pathways for Integrated Circuit and Similar Applications, and my publications "Polymer Precursor Synthesis of High T.sub.c Superconductors" appearing in Polymer Bulletin 21, 1-4 (1989) and "Polymer Precursor Synthesis and Characterization of YBa.sub.2 Cu.sub.3 O.sub.7-x ", Physical Review B, Volume 78, No. 6, 1 December 1988, p. 11853-6 relating thereto, a new polymer-metal-complex (PMC) precursor process synthesis of high-T.sub.c superconductors is disclosed, including ceramic oxide superconductors such as YBa.sub.2 Cu.sub.3 O.sub.7-x and the like comprised of crystallites of uniform and extensively interconnected morphology with important advantages over earlier ceramic methods including formation of the desired single phase, uniform grains of controlled sized, low sintering temperatures (&lt;910.degree. C. instead of &gt;950.degree. C.), shorter fabrication time (one hour, for example, instead of days) and free-standing film and solid fiber or filament structures.
In accordance with this process, the PMC is first prepared in which the various metal ions in desired stoichiometric ratio are homogeneously and uniformly complexed to the polymer, with the PMC precursor either cast into a clear film or spun into transparent fibrils. Under nitrogen, the organic polymer is pyrolyzed while the metal compounds react to form intermediate intermetallic compounds which are then converted, in the presence of oxygen, to form the desired high-T.sub.c superconductors.
It has now been discovered that this process can be applied to obtain usable hollow superconducting fibers with the attendant added advantages of the lightness, thinness and the hollowness, and with the potential supplemental and synergistic uses of the inner hollow space, including for conductors, reinforcing structures and for coolant purposes, among others.